Same thing for me. Caffeine only seems to boost capability in real terms when used sparingly (once a week or two). Otherwise, one becomes dependent on it and is simply medicating withdrawals which makes them feel like they're more focused when in reality they are simply no longer withdrawing. It's the classic drug addiction cycle but, given the comparative (with harder drugs) lack of serious side effects, it's generally considered to be safe. For people like me, however, the side effects outweigh the benefits 9 times out of 10 since it just makes me anxious and encourages fight or flight responses where they're not necessary.